The present invention relates to a high-voltage energy storage module for supplying voltage, in particular to a motor vehicle, and to a method for producing the high-voltage energy storage module.
High-voltage energy storage modules are used in vehicles for the sole or supplementary drive of the vehicle by an electric motor. In this context, a plurality of the high-voltage energy storage modules can be combined to form a battery. The individual high-voltage energy storage modules have a plurality of storage cells which are arranged in a row. Electrochemical elements, embodied, for example, as lithium-ion accumulators, are located in the individual storage cells. In the prior art, the individual poles of the storage cells in the high-voltage energy storage module are connected to one another by use of cables or rigid cell connectors.
An object of the present invention is to provide a high-voltage energy storage module which can be produced cost-effectively and in an automated process. In addition, the high-voltage energy storage module is to function in an operationally reliable fashion and with low maintenance. Furthermore, an object of the present invention is to provide a corresponding method for producing the high-voltage energy storage module.
This and other objects are achieved according to the invention by a high-voltage energy storage module for supplying voltage, in particular to a motor vehicle, comprising at least two storage cells and at least one electrically conductive connection between two poles of different storage cells. Electrochemical elements, preferably embodied as lithium-ion accumulators, are located in the storage cells. The storage cells preferably comprise a sealed housing in which the electrochemical elements are arranged. Two poles are formed on each storage cell. The poles are also referred to as connecting terminals. The poles of different storage cells are connected either in parallel or in series to one another by way of the electrically conductive connection. The invention provides that the individual connection is composed of a plurality of bonding wires arranged one next to the other. Each bonding wire is attached here to the two poles by a wire bonding. The wire bonding is a method for connecting a wire to a contact surface, for example to the pole of the storage cell. The wire bonding is also referred to as micro-welding. There is no need for any additional welding material or solder here. In order to produce the connection, part of the bonding wire is melted. This is done, for example, by applying ultrasonic vibrations to the bonding wire.
By using wire-bound bonding wires as an electrical connection between the individual poles it is possible to produce the high-voltage energy storage module in an automated fabrication process. This reduces the costs for the high-voltage energy storage module. At the same time, the bonding wires are relatively lightweight, with the result that a savings in weight can be achieved. The bonding wires conduct the main current, for example of an order of magnitude of 200 A. For this reason, a large number of bonding wires are correspondingly needed for one connection between two poles in order to make available overall a correspondingly large line cross section. The individual bonding wires are relatively thin and bendable, with the result that a flexible connection is produced which can compensate a certain length extension between the storage cells and is not susceptible to loads such as vibrations.
The high-voltage energy storage module preferably includes a circuit board having electronics for monitoring the storage cells. By means of the electronics, preferably comprising a CPU, the cell voltage and/or temperature of the individual storage cells can be monitored. The circuit board is preferably fitted onto the storage cells. By means of a corresponding embodiment of the circuit board, the circuit board can be used at the same time to center and/or to secure the individual storage cells with respect to one another. This allows for a savings in terms of additional components.
So that the electronics on the circuit board can monitor the temperature and/or the cell voltage of the individual storage cell, there is a need for an electrical connection to the circuit board in order to transmit a measuring current. Therefore, there is preferably provision that at least one of the bonding wires is attached between the two poles on the circuit board by way of wire bonding. The corresponding bonding wire therefore leads from one pole to the circuit board and from the circuit board to the next pole. In particular, the bonding wire on the circuit board is not interrupted, but merely connected by means of wire bonding.
Alternatively or additionally to the connecting of the bonding wire between the two poles, an additional bonding wire is preferably provided. The additional bonding wire is attached at one end to the pole and at the other end to the circuit board. The attachment to the pole and to the circuit board is in turn carried out by means of wire bonding.
The point at which the bonding wire or the additional bonding wire is electrically conductively connected to the circuit board is referred to as an attachment point. A temperature sensor is preferably arranged on the circuit board in the vicinity of the attachment point. The temperature sensor is designed to determine the temperature of the storage cell which is passed on via the bonding wire or the additional bonding wire. In order to determine the correct temperature of the storage cell, a corresponding calculation model is preferably implemented in the electronics on the circuit board. A phase shift between the measured temperature and the actual temperature at the storage cell can be taken into account by use of this calculation model.
The circuit board is of relatively thin design and preferably comprises a copper layer in the range from 10 to 100 μm. For the electrical connection of the entire high-voltage energy storage module there is therefore preferably a metal element positioned on the circuit board. This metal element is preferably an aluminum panel. A connecting device for a cable is provided on the metal element. The connecting device is preferably designed for the screwing on of a cable lug. Furthermore, an electrically conductive connection is provided between one of the poles and the metal element. This connection is composed again of a plurality of bonding wires arranged one next to the other. Each of these bonding wires is attached to the pole and to the metal element by way of wire bonding.
The bonding wires are dimensioned in such a way that they can be wire-bonded and readily bent into the required shape. For this purpose there is preferably a provision that the bonding wires have a round cross section with a diameter of a maximum of 1 mm, preferably a maximum of 750 μm, particularly preferably a maximum of 500 μm. As an alternative to this, the bonding wires are configured in a ribbon shape and preferably have a width of a maximum of 3 mm, particularly preferably a maximum of 2 mm. The bonding wires are advantageously produced from copper or gold, particularly preferably from aluminum.
The invention further comprises a method for producing the high-voltage energy storage module, comprising the following steps: (i) making available at least two storage cells, and (ii) forming at least one electrically conductive connection between two poles of different storage cells. A plurality of bonding wires are used in each case for the individual connections. The bonding wires are respectively wire-bonded to both poles.
In particular there is provision that during the wire bonding, the bonding wire is connected to the respective pole, to the metal element or to the circuit board by applying pressure, ultrasound and/or a raised temperature. The additional bonding wire is also correspondingly connected to the pole and the circuit board.
Preferably, no additional tool, such as, for example, a welding additive or a solder is used for the wire bonding. The bonding wire is melted and the conductive connection produced purely by applying ultrasound, pressure and/or temperature.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.